Extraction of mineral oils



Patented Aug. 30, 1932 UNITED STATES PATENT OFFICE SEYMOUR W. FERRIS, OF LANSDOWNE, PENNSYLVANIA, .ASSIGNOR TO THE ATLANTIC REFINING COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA EXTRACTION OF MINERAL OILS 1T0 Drawing.

The present invention relates to the art of mineral oil refining, and has particular reference to the separation of crude petroleum or petroleum products into fractions of different chemical compositions while of approximately the same distillation range.

In accordance with my invention, crude petroleum or petroleum products, particularly oils of substantial viscosity, are separated into various fractions by means of fractional extraction with an organic, that is, an aliphatic or aromatic thiocyanate or isothiocyanate or mixture of aliphatic and/or aromatic thiocyanates and/or isothiocyanates, or mixture of solvents containing substantial quantities of aliphatic and/or aromatic thiocyanates and/or isothiocyanates.

It is recognized in the art that mineral oils, such as petroleum. comprise essentially a mixture of hydrocarbons of various groups or homologous series of compounds, such for example, as paratfins of the general formula C H olefines of the general formula C Hg hydroaromatics and polymethylenes of the same empirical formula, and various other series of compounds of chain and/or ring structures in which the hydrogen to carbon ratio is less than in the foregoing series. A large number of individual compounds of each series and of differing boiling points are present in petroleum.

The various types of crude petroleum, which are generally classified into three groups, namely, paraiiinic base, naphthenic or asphaltic base, and mixed base, contain the various series of hydrocarbons mentioned heretofore in different proportions. For ex ample, in the paraffin base crude oils, such as those obtained from the oil fields of Pennsylvania. there is a relatively high proportion of hydrocarbons having a chain structure and a high hydrogen to carbon ratio, whereas in the naphthenic or asphaltic base crude oils, there is a relatively large proportion ofhydrocarbons having ring structures and a low hydrogen to carbon ratio. Mixed base crude oils, such as are obtained from the Mid-Continent oil fields. contain hydrocarbons in proportions intermediate these two extremes.

Serial No. 537,752.

As the use of practically all of the petroleum oils is almost entirely physical, the above described chemical nature of those oils is important in reflecting certain physical characteristics.

The variance in the proportion of the different series of hydrocarbons in parafiinic, naphthenic, and mixed base oils is evidenced by the physical properties of the various oils and particularly by the relationship of the specific gravity to the viscosity of one oil as compared with another. For example, oils derived from a Pennsylvania crude and having a viscosity of 400 seconds Saybolt universal at 100 F., will show a specific gravity at F. of about 0.878. Whereas an oil of corresponding viscosity produccd from a naphthenic crude, such as one from the Gulf coast area. will show a specific gravity of about 0.933 at 60 F. The relationship between the viscosity and gravity indicates degree of the parafiinic or naphthenic character of the oil.

If a given crude petroleum be distilled into successive fractions and the specific gravities and viscositics of the several fractions determined, it will be found that they conform to the general relationship:

in which G s the specific gravity at 60 F., V is Saybolt universal viscosity at 100 F., and a is a constant known as the viscositygravity constant. Fractions from each of the different types of crude have different viscosity-gravity constants. Such constants are lower for fractions of the paratfinic crudes than are the constants for fractions of the naphthcn c crudes. An article entitled The viscosity-gravity constant of petroleum lubrieating oils by .T. B. Hill and H. B. Coats which will be found in volume 90. page 641 et scq.. Industrial and Engineering Chemistry for June 1928. explains the dctermination of such constant for several typical oils.

The visco ity-gravity constant is, therefore. an index of the parafiinicity or naphthenicity of an oil, since when a given crude is distilled and fractions thereof are collected regardless of the fraction upon which the specific gravity and the viscosity are taken, when such specific gravity and viscosity are substituted in the formula and the viscositygravity constant of the fraction calculated, the constant will be substantially the same for each of the several fractions of the crude.

The viscosity-gravity constants of the viscous fractions for some of the typical crudes are as follows:

Milltown (Pennsylvania) 0.8067 Burbank (Mid-Continent) 0.8367 Guadalupe (Gulf coast) 0.8635 lHirando (Gulf coast) O. 9025 These oils are increasingly paraflinic as the viscosity-gravity constants decrease.

My invention is ba ed upon the discovery that oils containing both the paraliinic series of hydrocarbons and the various naphthenic series may be fractionally extracted with an aliphatic or aromatic thiocyanate or isothiocyanate. Methyl thiocyanate and/or allyl isothioeyanate are the selective solvents that I prefer to use. however. other aliphatic or aromatic thiocyanates or isothiocvanates such as phenyl thiocyanates may be employed. and are considered within the scope of my invention. The various s ries of hydrocarbons possess a difi'erential solubility in such solvents; the naphthenic hydrocarbons are much more soluble therein than the paraliinic hydrocarbons. By means of extraction with an aliphatic or aromatic thiocyanate or isothiocyanate, and more particularlv with methvl thiocyanate and/or allvl isothiocvanate. it is. therefore, possible to effect a partial separation of the naphthenic hydrocarbons from the parafiinic. and to obtain from an oil containing both classes of hydrocarbons. an oil which is much more naratliuic than the original oil and one which ismuch more naphthenic. By my invention, for example. it is possible to produce an oil of the quality normally obtained from Ap- T alachian crudes. from crudes of the mixdd base type from the Mid-Continent area. and conversely. to obtain oils from mixed base erudes such as are normally obtained from the napbthenic oils of the Gulf coast area.

In practicing my invention. I prefer to mix the oil fraction to he treated with a suitable proportion of an aliphatic or aromatic thiocyanate or isothiocyanatc or mixture of them, and more particularlv with methyl th ocyanate and/or al vl isothiocyanate. at a temperaturc suiiiciently high so that complete solution is effected and a homogeneous liquid obtained. I then cool the mixture to a temperature suiticiently low to cause a separation of the liquid into a twolayer system. the upper layer being a solution of a relatively small amount of the aliphatic or aromatic thiocyanate or isotbiocyanate in the more paraffinic portion of the oil, and the lower layer comprising a solution of the more naphthenic portion of the oil in the aliphatic or aromatic thiocyauate or isothioeyanate.

Instead of this heating and cooling to effect extraction, I may simply agitate the mixture of liquids at normal temperatures. Where substantially quantities of solid hydrocarbons belonging to the true paraliin series (C I-1 are present, these solids or waxes remain in the upper layer and may cause it to be solid or semi-solid. Separation of the two layers is then eflected, for example, by decantation, and the aliphatic or aromatic thiocyanate or isothiocyanate removed from each of the separated oil layers by vacuum distillation or other suitable procedure, thereby obtaining two oils of similar distillation ranges but of widely different physical characteristics and correspondingly different chemical compositions.

Before removing the aliphatic or aromatic thiocyanate or isothiocyanate from the upper and more paratlinic layerof oil obtained in the above described process, I may add a further quantity of aliphatic or aromatic thiocyanatc or isothiocyanate, and repeat the process for an extraction of additional naphthenic bodies from the oil. The extraction may be repeated any desired number of times, thereby producing oils of progressively increasing paraliinicity as evidenced by a decreasing viscosity-gravity constant. In waxbearing oils, the final undissolved product is a mixture of solid and liquid hydrocarbons. \Vhile the exact chemical compositions of these compounds are not known, it is probable that the liquid hydrocarbons are branched chain hydrocarbons of the paraflin series, whereas solid bodies are straight chain paraflin hydrocarbons. This product may be further separated into solid and liquid bydrocarbons by any of the well-known dewaxing processes, such as the cold settling process.

In many instances it will be found of advantage to dewax the oil prior to the extraction process. this expedites the manual operation of the latter.

My invention will he further understood from the following specific examples:

100 parts of a previously untreated distillate obtained from 2. Gulf coast crude oil and having a viscosity of 612 seconds Saybolt universal at 100 F., a specific gravity of 0.9303, and a consequent viscosity gravity constant of 0.874 was mixed with 100 parts of methyl thiocyanate and heated to slightly above the temperature of complete miscibility, which in the particular case was approximately 75 C. The homogeneous liquid which resulted was cooled with agitation to 35 C, and allowed to settle whereupon a two layer system formed, which consisted of an upper undissolved oil layer comprising 78.7 parts of the mixture and a lower layer of oil dissolved in methyl thiocyanate comprising approximately 121.3 parts of the mixture. After separation, the layers were each freed from methyl thiocyanate by vacuum distillation. The methyl thiocyanate dissolved fraction yielded 94.7 parts of methyl thiocyanatc and 26.3 parts of oil having a viscosity of 07 seconds Sayholt universal at 210 F., a specific gravity of 0.9854. and a viscosity gravity constant of 0.913. The undissolved fraction yielded parts of methyl thiocyanate and 73.4 parts of an oil having a viscosity of 381 seconds Saybolt universal at 100 F., and a specific gravity of 0.9042, and a viscosity gravity constant of 0.846.

100 parts of residual stock from a paraffin base crude having a viscosity of 103 seconds Saybolt universal at 210 F. and a specific gravity of 0.8905 and a consequent viscosity gravity constant of 0.808, was mixed with 300 parts of allyl isothiocyanatc and heated to slightly above the temperature of complete miscibility which in this particular case was approximately 23 C. The homogeneous liquid which resulted was cooled with agitation to 15 C., and allowed to settle whereupon a twolayer system formed which consisted of an upper undissolved oil layer comprising 90 parts of the mixture. After separation, the upper layer was freed from allyl isothiocyanate by vacuum distillation. This fraction yielded 24 parts of allyl isothiocyanate and 60 parts of an oil having a viscosity of 94 seconds Sayholt universal at 210 F., and a specific gravity of 0.8772, and a consequent viscosity gravity of 0.793.

From the above examples it will be seen that by a methyl thiocyanate and/or allyl isothiocyanate extraction there may be obtained oil fractions which are respectively higher in parafiinicity and naphthenicity than the original oil. By repetition of the extraction process upon the methyl thio cyanate and/or allyl isothiocyanate undissolved fraction, oils may he obtained which are increasingly paraflinic, as evidenced by progressively decreasing viscositygravity constants.

It is evident that my process is practically independent of the particular nature or source of the crude oil, and that there may be produced thereby oils of desired characteristics from oils which heretofore have not been used as a source of oils of such desired characteristics.

For example, my process may be employed to produce from petroleum ot a mixed base type such as would, on normal batch distillation, give a residuum with a viscosity of 150 seconds Sayholt universal at 5210 F. with a specific gravity of 0.928 or more. a lubricating stock with a viscosity at 210 l., of 150 seconds Saybolt universal, or more, and a specific gravity not higher than 0.910. This F latter combination of properties is typical of cylinder stocks produced from Pennsylvania crudes.

In extracting oils containing appreciable amounts of wax, such oils may be dewaxed, for example, by cold settling or centrifuging prior to carrying out the extraction. My process is operable. however, in the absence of preliminary dewaxing.

Hercinabove, mixtures of solvents have been referred to. it is to be understood that in such mixtures the constituent solvents will not react with one another, nor with the oil upon which they are to he used, and that such mixtures will contain substantial amounts of aliphatic and/or aromatic thiocyanates and/or isothiocyanatcs.

For brevity, in the appended claims, the term organic thiocyanate is employed in a generic sense to include one or a mixture of aliphatic and/or aromatic thiocyanates and/or isothiocyanates, or a mixture of solvents which contains substantial quantities of aliphatic and/or aromatic thiocyanates and/or isothiocyamites.

Also where herein and in the appended claims. an oil is specifically referred to as being viscous it is to be understood that the oil is of substantial viscosity, i. e., of the order of 50 seconds Saybolt universal at 100 F or more.

lVhat I claim is:

1. In the art of refining mineral oils, the process which comprises separating an oil containing paraflinic and naphthenic hydrocarbons into fractions respectively richer in parafiinic and naphthenic compounds by extracting said oil with an organic thiocyanatc.

2. In the art of refining mineral oils, the process which comprises fractionally extracting an oil containing parattinic and naphthcnie hydrocarbons with an organic thiocjanate to produce fractions of the oil rcspectively richer in paratlinic and naphthcnic compounds.

3. In the art of refining mineral oils, the process which comprises adding an organic thiocyanate to an oil containing paraiiinic and naphthenic hydrocarbons, heating the mixture to such temperature to effect solution, cooling the solution to form a two layer system, and separating the upper layer from the lower layer.

4. in the art of refining mineral oils, the process which comprises adding an organic thiocyanate to an oil containing paratliuic and naphthcnic hydrocarbons, heating the mixture to such temperature as to effect solution, cooling the solution to form a two layer system. removing the lower la yer. and similarly retreating the upper layer with an organic thiocyanatc.

a. 1n the art of refining mineral oils. the prm css which con'iprises bringing a mineral oil containing paratlini and naphthcnic hydrocarbons into contact with a thiocyanate,

thereby to effect solution of a portion richer in naphthenic hydrocarbons in the thiocyanate. separating the solution so formed from the remainder of the oil, and removing the thioeyanate from both portions of the oil, thereby to obtain fractions of the oil respectively richer in paiatiinic and naphthenic hydrocarbons.

U. The process for separating mineral oils containing paratlinic and naphthenic hydro carbons into fractions which comprises bringing the oil into contact with an organic thiocyanate. thereby to etfect solution of a portion of the oil richer in naphthenic hydrocarbons in the organic thiocyanate, sepa1'at-. ing the solution so formed from the remainder of the oil, and distilling the organic thio cyanate from both of the portions of the oil, thereby to obtain fractions of the oil respec tively iicher in paratiinic and naphthenic hydrocarbons.

T. In the art of relining mineral oils, the process which comprises bringing a mineral oil containing paratiinic and naphthenic hydrocarbons into contact with an organic thiocyanate, thereby to etlect solution of a portion richer in naphthenic hydrocarbons in the organic tbiocyanate. separating the solution so formed from the remainder of the oil. and retreating the oil remaining with additional amounts of an organic thiocyanate.

8. The method of producing paratlinic lubricating oil from mixed base crude which comprises distilling the crude and bringing a portion thereof into contact with one or more solvents from the group consisting of methyl thiocyanate and allyl isothiocyanat e, thereby partially dissolving the oil, sepa ating the solvent solution of oil so treated, and removing the solvent from the treated oil.

9. The process of producing a lubricating stock of specific gravity less than .910 and of Saybolt universal viscosity greater than 150 seconds at 210 F. from a crude petroleum which on normal distillation yields a residunm of 150 seconds Saybolt universal viscosity at 210 F. and a specilic gravity greater than .928, which comprises producing a residuum from the crude petrolem'n, and extracting said residuum from said crude petroleum with one or more solvents from the group consisting of methyl thiocyanate and allyl isothiocyanate.

10. In the art of refining mineral lubricating oil containing parattinic and naphthenic hydroczn'bons, the step of fractionally extracting the oil with one or more solvents from the group consisting of methyl thiocyanate and allyl isothioeyanate, to etfect a separation of fractions respectively richer in paratiinic and naphthenie compounds.

11. The process of producing a lubricating stock of specific gravity less than .910 and of Saybolt universal viscosity greater than 150 seconds at 210 F. from a crude petroleum which on normal distillation yields a residuum of 150 seconds Saybolt universal viscosity at 210 F. and a specific gravity greater than .928, which comprises separating a residuum from said crude petroleum and bringing such residuum into contact with one or more solvents from the group consisting of methyl thiocyanate and allyl isothiocyanate, to eti'ect solution of a portion thereof with the solvent, separating the solvent solution of oil from the portion which does not dissolve therein, and removing the solvent from the oil of said solution.

12. In a process for separating a. viscous mineral oil containing parafiinic and naphthenie hydrocarbons into fractions which are respectively richer in naphthenic hydrocarbons and paraliinic hydrocarbons other than wax, the step which comprises extracting the oil with one or more solvents from the group consisting of methyl thiocyanate and allyl isothiocyanate.

13. In a process for separating viscous mineral oil liquid at ordinary temperature containing paraflinic and naphthenic hydrocarbons into fractions respectively richer in paratiinic and naphthenic hydrocarbons, the step which comprises extracting the oil with one or more solvents from the roup consisting of methyl thiocyanate and sillyl isothiocyanatc.

14. In a process for separating a substantially wax free viscous mineral oil containing parallinic and naphthenic hydrocarbons into fractions respectively richer in paratiinic and naphthenic hydrocarbons, the step which comprises extracting the oil with one or more solvents from the group consisting of methyl thiocyanate and allyl isothiocyanate.

15. The process of treating a viscous fraction of a crude oil of one type containing paratlinic and napththenic hydrocarbons to procure a fraction having the quality of a corresponding fraction of a crude oil of differont type having a greater content of paraflinic hydrocarbons, which comprises extracting the viscous fraction with one or more solvents from the group consisting of methyl thiocyanate and allyl isothiocyanate, and separating the oil so treated into portions respectively richer in paratiinic and naphthenic hydrocarbons.

1G. The process of treating a viscous fraction of a mixed base crude oil to procure a fraction having the quality of a corresponding fraction of a parallinic base crude, which comprises extracting the viscous fraction with one or more solvents from the group consisting of methyl thioeyanate and allyl isothim-yanate, and separating the oil so treated into portions respectively richer in paratlinic and naphthenic compounds.

17. In the art of refining mineral oils, the process which comprises adding one or more solvents from the group consisting of methyl thiocyanate and allyl isothiocyanate to a viscous oil liquid at ordinary temperatures containing paraflinie and naphthenic hydrocarbons, heating the mixture to a temperature sufficient to efi'ect solution, cooling the solution to a temperature suflicient to form two layers respectively richer in naphthenio hydrocarbons and paraflinic hydrocarbons other than wax, and separating the upper layer richer in paraf'finic hydrocarbons from the lower layer richer in naphthcnic hydrocarbons.

18. In the art of refining mineral oils, the process which comprises adding one or more solvents from the group consisting of methyl thioeyanate and allyl isothiocyanate to a viscous oil liquid at ordinary temperatures containing paraflinic and naphthenic hydrocarbons. heating the mixture to a temperature sufiicient to eifect solution, cooling the solution to a temperature suflicient to form two layers, separating the solvent and paraflin Wax from the upper layer, and separating the solvent from the lower layer to produce one fraction richer in paraifinie and a second fraction richer in naphthenie hydrocarbons than said viscous oil.

In testimony whereof I aflix my signature.

SEYMOUR W. FERRIS.

CERTIFICATE OF CORRECTION.

Patent No. 1,874, 947.

August 30, 1932.

SEYMOUR W. FERRIS.

It is hereby certified that error appears i above numbered patent requiring correction as n the printed specification of the 5, for the article "a" read an organic; page 4, claim 5, line 2. after "the", and line 4, after "the" second occurrence, insert the word organic; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 29th day of November, A. D. 1932.

(Seal) M. J. Moore, Acting Commissioner of Patents.

thiocyanate and allyl isothiocyanate to a viscous oil liquid at ordinary temperatures containing paraflinie and naphthenic hydrocarbons, heating the mixture to a temperature sufficient to efi'ect solution, cooling the solution to a temperature suflicient to form two layers respectively richer in naphthenio hydrocarbons and paraflinic hydrocarbons other than wax, and separating the upper layer richer in paraf'finic hydrocarbons from the lower layer richer in naphthcnic hydrocarbons.

18. In the art of refining mineral oils, the process which comprises adding one or more solvents from the group consisting of methyl thioeyanate and allyl isothiocyanate to a viscous oil liquid at ordinary temperatures containing paraflinic and naphthenic hydrocarbons. heating the mixture to a temperature sufiicient to eifect solution, cooling the solution to a temperature suflicient to form two layers, separating the solvent and paraflin Wax from the upper layer, and separating the solvent from the lower layer to produce one fraction richer in paraifinie and a second fraction richer in naphthenie hydrocarbons than said viscous oil.

In testimony whereof I aflix my signature.

SEYMOUR W. FERRIS.

CERTIFICATE OF CORRECTION.

Patent No. 1,874, 947.

August 30, 1932.

SEYMOUR W. FERRIS.

It is hereby certified that error appears i above numbered patent requiring correction as n the printed specification of the 5, for the article "a" read an organic; page 4, claim 5, line 2. after "the", and line 4, after "the" second occurrence, insert the word organic; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 29th day of November, A. D. 1932.

(Seal) M. J. Moore, Acting Commissioner of Patents. 

